The majority of hand knotted and woven rugs are made with a cotton foundation and wool face yarn. These natural fibers have several characteristics that require far different cleaning techniques than what is commonly used to clean synthetic wall to wall carpet.
The outer layer of wool (the epicuticle) is made of overlapping scales, a marvelous design that allows the fiber to hide large amounts of soil. The downside is that often rugs are allowed to develop a deep and heavy build up of soil. Specialized dusting equipment and techniques that can only be performed in a dedicated rug cleaning facility are needed to remove this soil.
Temperature and Chemistry
Wool has a wonderful ability to take dye. This is why wool rugs often have such beautiful, rich colors. However, high temperature and aggressive chemistry (typically used in cleaning wall to wall carpet) can cause these dyes to crock and bleed. Damage to the wool itself can also occur. Wool needs to be cleaned with cool water and neutral non-ionic shampoo that is specially designed for natural fibers.
Far too often, fine rugs are damaged by the use of bleach in the cleaning process. Bleach actually dissolves wool and it is very damaging to cotton. Many rug cleaners use bleach to whiten fringes. It is also used by some who use large wash tubs to clean rugs. They use bleach to control cross contamination as rugs are co-mingled in these tubs and they use the same water over and over.
Wool can absorb 30% of its weight in water without even feeling damp. Compare this to nylon (5%) or polyester (1%). Cotton is 10 times more absorbent than synthetic fibers. This one characteristic of wool and cotton changes the cleaning requirements more than any thing else.
1. Synthetic fibers absorb very little water, so a relatively small amount of water is needed to clean these fibers. By contrast, wool and cotton require copious amounts of water for effective cleaning and rinsing to occur.
2. Since cotton and wool holds so much water, far greater extraction is needed than what carpet cleaning systems can provide to remove any remaining soil and rinse water. Rinsing these fibers is much like rinsing a sponge. It requires several exchanges of fresh water. Without highly effective water removal, cleaning is compromised.
3. Even with efficient water removal, if left to dry on their own, wool rugs will take far too long to completely dry opening the door to potential problems. A drying room with the right temperature, low humidity and air movement are needed for rapid drying.